1. Technical Field of the Invention
The present invention relates to a drill polishing method and a centering tool therefor in the field of machine tools and drilling. More particularly, the present invention relates to a drill polishing method and centering tool therefor capable of polishing precisely by accurately centering the drill to be polished.
2. Description of Related Art
Hitherto, U.S. Pat. No. 3,553,898 and Japanese Patent Publication No. 1-46266 have been known as drill polishing machines for polishing the tip of the drill used in a machine tool or drilling.
However, according to the U.S. Pat. No. 3,553,898, the drill is inclined by a specific angle on the rotary shaft of the grindstone and is moved on the slide, and the drill holder must be held in hand while sliding. However, after polishing one tip of the end of the drill, the drill must be detached, inverted by 180 degrees and polished again. This has taken too much time and labor, and the precision was not sufficient.
According to the latter Japanese Patent Publication No. 1-46266, in addition to the above type, a holder for holding the drill is supported on the slide base by rotating 180 degrees. Therefore, the efficiency of the drill polishing job is enhanced.
In these drill polishing methods, nevertheless, the drill holder shaft is set at a specific angle on the rotary shaft of the grindstone, and it is intended to polish while setting the tightening surface of the drill holder at a specific angle to the horizontal plane.
Accordingly, not centering accurately on the basis of the spiral grooves at both sides of the drill to be polished, it was difficult to polish the flank or thin the chisel always at a specific angle to the chisel.
The present applicant already proposed, in Japanese Patent Application No. 7-345599, a method of polishing the flank of the drill tip and thinning the chisel, in one chucking operation, the drill to be polished. However, since the chisel width differs from the diameter of the drill, it was difficult to polish by centering the drills differing in diameter accurately.